Current transformer test device and method

Abstract

A current transformer test device and a method implemented using the test device, is useful to verify proper CT installation and operation, and does not rely on the generator (or other system) to be in a state of relatively high assembly. The test device allows a current transformer to be tested by supplying an alternating current (AC) signal to a primary winding of the current transformer to thereby induce an AC signal in a secondary winding of the current transformer. The test device is used to simultaneously monitor the phases of the supplied AC signal and the induced AC signal so that a determination can be made as to whether the current transformer secondary winding is properly installed relative to the current transformer primary winding, and to simultaneously monitor the current magnitudes of the supplied AC signal and the induced AC signal so that the turns ratio of the current transformer can be determined.

1. A current transformer test device for testing a plurality of current transformers each having at least a primary winding and a secondary winding, the test device comprising:
 an alternating current (AC) power source configured to supply an AC signal having at least a current magnitude; 
 an AC current meter configured to measure and display the supplied AC signal current magnitude; 
 a current transformer primary winding select switch movable to one of a plurality of switch positions, each switch position corresponding to one of the plurality of current transformer primary windings; 
 a current transformer primary winding test jack coupled to receive the AC signal from the AC power source, the current transformer primary test jack configured to be releasably coupled to each of the current transformer primary windings and, upon being coupled thereto, to supply the AC signal to the current transformer primary winding that corresponds with the switch position of the current transformer select switch; and 
 a current transformer secondary winding test jack configured to be releasably coupled to each of the current transformer secondary windings and, upon being coupled thereto, to receive a current transformer test signal from one of the current transformer secondary windings when its associated current transformer primary winding is supplied with the AC signal. 
 
   
   
     2. The test device of  claim 1 , further comprising:
 a secondary winding test device node adapted to be coupled to a test device; and 
 a current transformer secondary winding select switch coupled between the current transformer secondary winding test jack and the secondary winding test device node, the current transformer secondary winding test select switch configured to selectively couple one of the current transformer secondary windings to the secondary winding test device node. 
 
   
   
     3. The test device of  claim 2 , further comprising:
 a plurality of burden resistors coupled between the current transformer secondary winding select switch and the current transformer secondary winding test jack. 
 
   
   
     4. The test device of  claim 2 , wherein the AC signal further has at least a voltage magnitude, and wherein the test device further comprises:
 a primary winding test device node adapted to be coupled to the test device; and 
 an AC signal parameter select switch coupled between the AC power source and the primary winding test device node, the AC signal parameter select switch moveable between a first position, in which a signal representative of the AC signal current magnitude is coupled to the primary winding test device node, and a second position, in which a signal representative of the AC signal voltage magnitude is coupled to the primary winding test device node. 
 
   
   
     5. The test device of  claim 1 , further comprising:
 a plurality of solenoids, each solenoid coupled between the current transformer primary winding select switch and the current transformer primary winding test jack and including:
 a contactor coupled between the AC power source and the current transformer primary winding test jack and movable between an open position and a closed position, and 
 a coil configured to be selectively energized based on the position of the current transformer primary winding select switch and operable, in response to being energized, to move the contactor to the closed position and thereby couple the AC signal to the current transformer primary winding test jack. 
 
 
   
   
     6. The test device of  claim 5 , further comprising:
 a direct current (DC) power source coupled to the current transformer primary winding select switch and configured to supply DC power to one of the plurality of solenoid coils based on the position of the current transformer primary winding select switch. 
 
   
   
     7. The test device of  claim 1 , wherein the AC power source is a variable AC power source. 
   
   
     8. The test device of  claim 7 , wherein the variable AC power source comprises:
 a variable transformer having variable turns ratio, the variable transformer including a variable primary winding coupled to receive an AC input signal, and a secondary winding adapted to supply the AC signal; and 
 a user input coupled to the variable primary winding and configured, in response to a user input, to vary the turns ratio and thereby vary the AC signal current magnitude. 
 
   
   
     9. The test device of  claim 1 , further comprising:
 an AC voltage meter configured to measure and display a voltage magnitude of the supplied AC signal. 
 
   
   
     10. The test device of  claim 1 , further comprising:
 one or more load resistors coupled between the AC power source and the current transformer primary winding test jack. 
 
   
   
     11. The test device of  claim 1 , further comprising:
 a test device coupled to receive and simultaneously display signals representative of the AC signal and the current transformer test signal. 
 
   
   
     12. The test device of  claim 1 , further comprising:
 a main power switch coupled to the AC power source and adapted to receive an input AC power signal, the main power switch movable between an on position, in which the AC power signal is electrically coupled to the AC power source, and an off position, in which the AC power signal is electrically decoupled from the AC power source. 
 
   
   
     13. The test device of  claim 12 , further comprising:
 a second power switch coupled between the main power switch and the AC power source and movable between an on position, in which the main power switch is electrically coupled to the AC power source, and an off position, in which the main power switch is electrically decoupled from the AC power source. 
 
   
   
     14. The test device of  claim 13 , further comprising:
 a first indicator configured to receive an energization signal when the main power switch is in the on position and the second power switch is in the off position; and 
 a second indicator configured to receive an energization signal when the main power switch and the second power switch are both in the on position.